Views text area plugin does not declare a dependency on the text format it uses

Problem/Motivation

This was uncovered by #2916898: Do not use basic_html text format for 'No log messages available.' message.

If you add a custom text with a text format to a views area (for example the empty text of many views), the view will not have a dependency on that text format, so that it will break when that text format is missing.

Proposed resolution

Add a dependency on the text format.